Electric switch mechanism



vMmh l13, 1945.

|. E. MCCABE ELECTRIC SWITCH MECHANISM u 5 Sheets-Sheet 1 'OriginalFiled March 19, 1940 a w l B l E E ,van n., 3L nog z u l www: m n a/NsuL/l TlaN INV ENT OR. IRA E MC C085 N m v A L u s w ATTORNEY.

`Mmh 13, 1945.

DE. MCCABEk ELEQTRI-c swITgH MEGHANISM Original Fil'ed MaiGl'lN 19, 19403 Sheets-Sheet March 13, 1945. 1 E MCCABE 2,371,455

ELECTRIC SW1-TCH MECHANISM I Original Filed March 19, 1940 3Sheets-Sheet 3 l INVENTOR. /RA E MQ cass Y ATTORNEY.

' Patented Mar. 13, 1945 such.' an. extent astoelibst'iamti'alitz.supersede.I the (iemand. coallfurnaces-j whereverY.ele ctricity .is available.. It wasmecognizedearly inthis.indus`. trythat the burner mechanisms'trnustf-be :automatic. inV operation. and. socontrolled...as. Yto furfuel'.. When heat.,was' desired".andlto shut-.ofi the, delivery of.- i1e1'.when.the...demand` for` heat lwassatised"..as..a. normali operation, andlat .the same time. to. provide.safetyA vmeansit'o. cut the suppl)7 ,offuel upon ananormalloccurrence,suchl .as f iitial-lffaililre.. of. .therfel to .ignite or failure. of.combustion during..normal-operation. f The. popular` demandor. such..heating Asystems has heen'. enhancedlyf the 'developments'. of. the.

fluidie vturnenman-utacturens. in. reducgV the cost. of' the burner..mechanismtolbe .withif the i reach ofl ,the generali 'publica 'llhelreduction.. of cost,y :'was.. a.v mechariicalp riol'ent. .to the. burnermanufacturers, but, as. `ther.j.hurner}mechanisins were. operated. by.,electricityf .the probleurof. au tomatic` safety. control.. was; anelectrical. prob# lem. A controlyihdl'stryrgrew upfseparate `anddistinct from. .the .Burnerllmanufacturerswhich encounteredl a..muclmore .diili'yultr problem... So that today While.y theudifuehburners ar e.ad-`

houses, the .controls .for trie v.burners arer oimoli.- cated;4 costly.,anti`.require.especially.4 tranedpersonnel to instalLlthemi511.connection.WithiV the hurner. The accepted typef.of..safty`'controls' ofthis character is usually.l responsive. toV the pres. enceor: absenceoitheheatof combustion within', the. heater or furnace..and.usua11ir;requires,.a member of. thermostatic..metaljfmounteilih thestack leading from. the heater -t`.`.the.chimriey or ina.-.position.otherwise. adjacentftothecombuston chamberdsassociatedrwithgthe.burger mechanism andi;is=dntadtiitionftmtheroom.thenmostat for controllingAzhe.-normalioperation,l.

It is an objectf .this inventiomto-.provide a safety conti-ot for :anelectricallmoperated au@ controlled; uidf.k .fuel. burner.mechauism`-which will providethersafety 1mzhanisr-|qi wttmn asmalt(Cinese-zit of enclose@ space,y sof constructed; at. the factoifglas torequire no further'adjstmehmmreventhg the Q0 changes maybemadewthoutideparting.'from the n'responseto the Figure is a wiringdiagram illustrating the 1 applicationV of this improved switch, shownin Figures l to 3, to a control circuit of an automatic fluid fuelburner. i

Figure 6 is a detail view partly in elevation and partly in section of aswitchre-set mechanism, comprising a form of push button switchincorporated in the control system, as disclosed in Figure v5.

Figure '7 is a view similar to Figure l of a modified formjof thisinvention.

Figure 8 is a view similar to Figure 3 of another modified form of thisinvention, including an automatic magnetic re-sei; device.

Figure 9 is a view partly in section, taken on the line 9-9, Figure 8.

VFigure 10 is amodied wiring diagram similar to vthatV vdisclosed inFigure 5 and wherein the improved vswitch is mounted upon the air pipeof the burner and a modiiied form of manually operatedv magnetic re-setvdevice is employed.

YIn carrying outthe present invention it is preferable` to enclose themoving parts of this safety control in'a spherical transparent bulb orcasing I, similar tocthat disclosed in Figure 8 of the applicants priorPatent No. 2,162,098, June 13,1939. The bulb I is preferably of glassprovided with a radial extension through which the leading in wires 2, 3and l are sealed and the bulb diametrically opposite the seal isprovided with aradial well 5'for containing mercury or other fluidelectrical connecting material 6.

normally urged out of engagement with the mercury 6, as hereinafterdescribed.

The electrode 'I supports a member I2, preferably by a bracket ofinsulating material or glass bead I3 mounting a spring latch I4terminating lin a glass bead or cylinder of insulating material I5normally urged in the direction of the rotatableextension II of theyelectrode ID, to ride over and fhold the extension Hfwhen rotated toengage the mercury B, as shown in Figure 2. The electrode 'I alsosupports a coil I6 of bi-metallic metal within the heating coil 8 by abracket I1 secured to the Vouter free end of the coil I6, as shown inFigures l and 3. The inner end of the coil I6 is secured to the end of ashaft I8 and supportsthe shaft in a horizontal plane. The other end ofthe shaft I8 is secured to the inner end of'another coil' I9 ofbi-metallic metal, which responds oppositely and moves in an oppositedirection to coil I6. The outer end of coil I9 carries a latch release2U normally touching the latch I4 when theicircuit to the leads 2 and 3is closed and the electrode extension- I I is immersed in the mercury.When the circuit is closed through the leading in wires 2 and 3, as bythe room thermostat as hereinafter described, the relation of theresistance wire coil 8 and the thermal coil I6 enclosed thereby is Suchthat the predetermined time allowed for the ignition of the burner flamemaylapse before the coil I6 responds to the heat of the coil 8 to rotatethe shaft I8 sufciently to cause the latch release 20 to tripthe latchI4 to release the terminal extension II to be moved out of engagementwith Since the circuit 'is made and broken through the mercury connectorthe switching mechanism is of the mercury tube switch type and thereforethe casing is evacuated andthe air is replaced by an `inert gas'. Thelconductivity of such gas affects the operatingcharacteristics'of thedevice and it has been found that the use o f argon permits a smaller-sitze bulb to be used. As shown in Figures 1,2 and 3, the leading inwiresJ 2, 3 and 4 extend beyond the end of the seal and the projectingends of leads 2 and 3 are adapted to be connected to the conductors ofthe circuit to be controlled by thesafety switch mechanism, while the-projecting'end of lead; 4 is adapted to be connected 4to the conductorofV the circuit for manually resetting the switching mechanism. Theleading in wire 2 upon the interior of the bulb I is connected to anelectrode l which includes intermediate its length a coil 8 ofresistance wire arranged concentric with the horizontal axis of thebulb' and the end 9 of the electrode isextended in `a-vertical positionto approximately the bottom of -the well 5 so that its lower end will beimmersedin the mercury 6. When the circuit is completed and the currentiiows through the resistance coil 8 the coil will become heated.

The leading in wire 3 upon the interior of the bulb I is connected to anelectrode I0 which terminates in an extension I I, the free end of whichis adapted to enter and engage the mercury 6 to complete the circuittherethrough and is 75 the mercury 6 and open the circuit through thesafety switch bulb I.

In accordance with this invention'the safety control bulb I is solocated that in the event the ignition of the combustible mixture of theburner takes place within the predetermined time, the flame of theburning fuel will fall upon the bulb I.' As disclosedin this applicantsprior Patent No. 2,162,098, June 13,- 1939, the bulb I is provided witha reiiector I? to concentrate the rays of light from the burner ame uponthe thermostatic coil I9, as shown in Figure 1, to increase itstemperature and cause its `1'esponse thereto to counteract the eiect ofthe rotation of the shaft I 8 imparted bythe coil I6 and cause the latchrelease 2Iltov remain in neutral position. Likewise the thermal coils I6and I9 will compensate for changes in ambienttemperature to prevent thelatch I4 being abnormally released.

This invention also contemplates a. means for resetting the switchmechanism within the bulb I when the latch I4A has'been released byinitial failure of the combustible-mixture to ignite and provide aburner flame or upon failure 4of the combustible mixture during normaloperation. A preferred form of "this rfc-setting mechanism isillustrated in Figures 1,' 2l and 3. As shown in'Figures 2 and 3,theelectrode 2l, attached to the end of theleading inwire 4 within the bulbI,wis arranged to extend in parallel and spaced apart relation to theelectrode I0 so that the lower ends may support between them acup-shaped shell'22 Vof refractory material. `A coil 23 of resistancewire is wound about the shell, embedded :in thewalls of the shell orarranged upon the' inner walls ofthe shell, as may be desired, and isshown in dotted lines in Figure l as embedded within the vwalls of` theshell. The opposite ends-of the coil23 are connected tothe lower endso'f-jthe electrodes I Il and 2| so that when the circuitis-fopenf-through the nerarc connector the.. cosinel ot. a.. circuit..

. befweealeadinaimwirs iced.Lmeribisofthe shown in. Figures-` 1, and 2.,and'. secured to outer endofY the. coilv 2`4',`.at. its lower.'endQV Theinner end of the coil. Mlist securedlto ashaitff..

25. and. holds.` the .shafft inl ahorzontal. position. Abi-metalliccoilY 2&1'. mounting.. the extension.. I. Il; of.` theelectrode. Imat-its .outer free end .is secured.. at.. it s inner..l end. tovl theopposite endg olf-the .shaftg changesin ambient temperaturesothathogmoveg ment of. the extension IQI.,` will take placempon changesin. ambient temperature-. When? t1he e x .j tension. II is.. out.. of;engagement` with the. mer,..- cury the. closing, of the circuit'.through. leading.; in. wires. 3. and 4Qwll heat thecoil'ofresistancewire 423 and. the. .heat will .be/transmitted' to the.. bi-metal1iccoil. 24 within thecupshaped1- shell. 22. and. in. response. theretowill. rotategthe..shatt Zuf and coil 2.1` to.. move theextension.III1toA cause its .end to enter andi beg.submelsgedm`vvithifnthe mercury. 6. The extension I I. is.v providedv w" 'h a'.shoulder 2'8whichV willy allow' the insulatedjfend I5 of the latchI41to.` engage. the,.shoulcleicfZil'v` and hold` the extension; IlI. offthe electrode. IU immersed. in; ther mercury to establish the circuitthroughleading .in wires. 2 and3 Wi,tl'iinj,thel bulbe Ir A-fterthelatch I4 locks theextension.. Illini the. -closedpositionand current.passes` through, the-leading in wiresi2 and' 3 A.the current.through..ther. heating. coilY 2'3` is short-circuito@and,V the. cooling.- of the.coil 2541 places. lcoi1` 2.T und'er .sufi. cient tension. to snaptheextension. I'I,.' w.`r'1en.v released, to open thecircuit thro1.1gh.tliehier 4 cury 6`. j

A#t.modification of.l this form of switch mecha-L nism is illustrated inl'igure. 4 ini which .the circuit.` is closed. through. metal1 contactsZ9` .andfl carried` by the extremitiesofthe nortionQ .oftheelectrode. 1. andthe .extension II. of the electrode.v I; In. this gurethepartsare illustratedih. the positionv assumed after the. latch I4'.has. been. moved by the latch release 2l1`toride.;.out, of." engagementwith the shoulder .28.. of .the electrode extension II. so that the coilZlhas separated4 thecontacts 2s andan.. nl this position 'incita-.cnMcis held. inoperative. by the.. insulating cylinder I` engaging theportionof. theextension. Lllbef.-

low the, shoulder. 28,. asshown, c

To illustratea preferred meansior operating; theY vire-setting`mechanism;. Figure. 5. shows.. a. schematic diagram. of a typicalinstallationoia. commercial fluid.. fuel burning: systemg and a.wir.ing` diagram thereof. in which F ;indca tes.th e combustion chamber of;a heateror furnace to4 which .isz installed. an electrically operatedoil. burner B--the .operationof. which; is controlledfby room".Athermostat T.' All commercialoilburnersg include; a recognized L means for igniting the fueLj vOne of.; theA wires of. the.4 commercial electriccurrenthisconnected to the binding post- 311i The current. passes .from,there through-a motor swtch MS; preiera'hlyva mercury tube svvitclnand4from; there through.- bindi'ng .post 32,throughwire;;33g o-one.E Sideofrthei motornof therburnerfBa The; other' side of. the' motorisconnected: by: the wire.: 34 tc theibi'nding post351andlfromnthencento;the; oth'emw-lre of; the?. commerciali-aumentaVThe @commenti/ta-ispreferarla controleur.. a.

r@9111 ..thermostatthrbugh a repulsion relay.' which..

isga.v commercial' product.. such.. as shown in applicantsprior PatentNo.. V2.,02?l=,69.7,. December. 1.7311935.. One end of ,thestationaryprimaryf coil. BCfisconnectedto. bindingI post 3.I and the.other end; to.the-bindingfpostSB.. Oneend of thewind.-ingsiotvthesecondary coil SC is.l connected tothe:` bindngpost'l andtheother. endto the binding post 13.8;V The binding; posty 3.1 -isIconnected by;

the wire..39. totheleading in.wire 3 of the safety, svvitch.bulb I..Thelead-ing in wire ofthesafety: switch bulb; I` is connectedby the.wire 411,130.A a. binding. post. 4-IrwhichinIV turn` is connectedv by.

them/ire 42.y toene. sideof the= room. thermostati'l,

theother side. @t which is connected by wire 43`r to.- theqbindng. post38.jso. that lwhen-the circuit` is. normally closed'ozthrough the.fluidconnector, 6. withinthe safety bulb. Ig, as. hereinabove desclibedg. the circuit A,tlfiroughthe secondary coilSCwillfbecontrolledby.- theroomthermostat T. The` motor4 switch.MS ismounted onan` .arm pivoted to.. .the vertical. core VC. at ythegsideopposite the movable secondary .coil of the.v relay R which is.

secuisedto theother. endofgthe arm and. so vaitrangedthatwhen the.secondary coil. is'. d`e` energizedit will. tilt the. mercury tubejmotor switchlMS into.the open.position. When thecir. cuite, throughtheVv secondaryx coil. SC, isclos'ed by the room. thermostat itisrepelled and Will tiltthe motor;` switch. into v.closed.posit-ion,A as.shown in dottedflines, to closeathe. circuitto. the, motor. Ifcombustion failseithen yinitially or during normal. operation the burnerflame.becomesextnguished` and the `saletyswitch. mechanism within. thelbulbV If will open. the lsecondary. circuit, ,ifclosed. by the. roomthermostat,- throughf the. mercury 6.4 and. cause thesecondarycoil tofall and. open the.

motonswitch. Inord'er. to re-set the safety'switch.`

mechanismV Within.- theA4 bulb I` itis preferableto mount a manuallyoperable switch actuator. uponf the` casing. 44. which covers thecommercial relay Rand is shown in the detailed' view in Figure'.,

An arm 45is.mounted. atthe pivotalpoint' ofthe arm carrying, thesecondarycoil:` S'Cfandmotor. switch MS to extend upwardly above the.corev of.' the; relay.R,. the. free, end" off which will be moved'.fromthev position. shownin full. lines in Figuref. when the. relay .isAde-energized. to open. the. motor' switch. to the.. position shown. in.dottedilines in.V Fgure when the relay has been energizedito, close themotor switch. Thisarm mountsa bind#y ing post andcontact 46Yadjacent-its free end, as. 1 showny in. Figure 6. This bindingpostand.con-v tact is connected by wire. .41.' .to .binding.pos`t 4'81 andzfrom thence bywire 49. totheleadingin wire. 4 of .the safety switch bulbI. A.A contact50`-is mounted upona binding. post 5I` to be. engagedby.

the :contact 46.- .when the arm.. 45.l is in the. position shown. indotted lines. in Figure 6` and therelay R is de.-energi Zed.and themotor switch MS open.. The contacts.. 46 and 50 arenormallyheld'v .in-

spacedA apart-.relationby .constructing vthe arm 45"ofresilientmaterial.A The bindingpost 5I. isco'nw nectedbythe wire. 52tok thebinding post. 4I... 'I'.hel

manual re-set. actuator includes a springfpressedl plunger 53 includingya reciprocating, pinf5`4l so located that whenthe4 arm. 45 is inpositionw-ith. the. contacts 46 and 50 in alignment. the manual;depression. of the plunger 53. will. cause the enel` of the pin. 54 toengage the upper freeendiof.

- thearm 45 and move-the contact46 -into.engag a kr ment with thecontact; 50 and therebycom-pletev the.- circuitf'from the ,contact 46through; wires;l

41;.; 49; 'leading f infzwire .4,. through-i electrode; 21.-;-

4Y I i heating coil 23, electrodeA Ii), leadingV in wire 3, wire 39 andthrough the secondary coil of the relay to binding post 38 and fromthence through' wire 43, room thermostat when closed, wire 42 to bindingpost 4I, and to contact 56. In order to maintain this circuit closed asuicient length of time furthe heating coil 23 to return the extensionII of electrode I into engagement with the mercury 6 a pivoted latch 55is provided having a hooked end adapted to ride over the free end of thearm 45 as it is bringing contact 46 into engagement with contact 50 andto hold it with the contacts in engagement until the movement of thesecondary coil SC carries the end of the arm 45 out of engagement withthe latch 55. It is necessary that the resistance of the heating coil 23is such that although the secondary circuit is closed therethrough,suiicient current will not pass through the secondary coil 'to repel it.As the latch I4 would not release the extension I I of the electrode Into open the circuit within the safety switch bulb I unless there was aame failure, the secondary circuit would be closed through the roomthermostat so that as soon as the coil of resistance wire 23 producedsufficient heat to return the extension II into contact with the mercuryto close the normal circuit through the room thermostat, safety switchmechanism within the bulb I, and secondary coil SC, the coil SC will berepelled by the full secondary current to move contact 46 out ofengagement with contact 56. As soon as the secondary coil has beenrepelled the free-end of the arm 45 will be released from the latch 55and thereafter when the secondary coil lsvdeenergized by the opening ofthe room thermostat the end oi the arm 45 will return with the con-.tacts 45 and 59 in spaced apart alignment with ton 53 fail to returnafter being depressed, the

neXt time the secondary circuit is opened the edge of the arm 45 willengage the rod 54 as the coil SC falls and will prevent the contacts 46and 50 being aligned with each other and render the reset mechanisminoperative until the push button 53 is released to return it to itsnormal position.

Figure 7 illustrates a modification of the safety switch mechanism shownin Figures 1, 2 and 3 wherein it is possible to dispense with the coilof resistance Wire 8 connected in the electrode 1. In this form theelectrode l is; connected by a bracket 56 directly to the outer free endof the thermal coil I I6 and the portion 9 of the electrode 'I enteringthe mercury 6 and submerged therein is supported by a bracket ofinsulation or glass bead l upon the electrode 'I and the latch releaseis connected by wire 58 to the portion 9 of the electrode l. By soconstructing the parts when the circuit is normally closed through themercury 6 and the room thermostat closes the circuit through the leadingin wires 2 and 3, the current passes through electrode l, thermal coil Ii6, shaft I8, thermal coil Iii?, latch release 20 and wire 58 totheportion 9 of the electrode 1. In this case the lthermal coils H6 andH9 are so constructed that they respond alike to changes in' ambienttemperature, but diier in electric resistance whereby the passage of anelectric current through both will cause coil II6 to deform more rapidlythan coil IIB, as disclosed in this applicants prior Patent No.2,149,853, March 7, 1939, but the reected rays of light from the flameconcentrating upon coil IIS will cause coil H9 to deform at the samerate but in the opposite direction to the coil IIS so that the movementof the two coils balance each other. y

Another modification is shown in Figures 8 and 9 whereby the re-settingmechanism may be constructed to dispense with the leading in wire 4,electrode 2 I, heating coil 23, thermal coil 24, and shaft 26, as wellas the circuit opened and closed manually through contacts 46 and 5D,shown in Figures 5 and 6. In this form `the inner end ofv the coilspring I2'I is carried by the lower end of the electrode I0 and theshoulder portion 28 of the extension I I is provided with an extension59 of magnetic material. The free end of this eX- tension or armature 59is formed to follow the general contour of the wall of the bulb I and beadjacent thereto when the electrode extension I I is in'enga'gement withthe mercury 6. When the latch I4 has released the extension I I, tovoperi the circuit by being moved out of the mercury 6, the positionassumed by the armature 59is shown in dotted lines in Figure 8.

One means for re-setting the switching means so constructed is toprovide a iixed magnet 66 mounted on the free end of a iixed spring Siso mounted that the magnet will be normally held a suiicient distancefrom the bulb I so that the magnetic iield of the magnet will notattract the armature 59 when the circuit through the mercury 6 is open.The free end of the spring 6I may be readily advanced to move the magnet60 to'bring the armature 59 within its magnetic iield to return theextension I I to its latched closed position. l

Another means to re-set the switch mechanism of this type is by the useof an electro-magnet which will allow the re-setting of the switchmechanism to be actuated at a point remote from the burner mechanism.Such a means is shown in Figure 10 in a schematic diagram of a heatingsystem and wiring diagram including another form of installation.

In Figure I0 the furnace or heater F is pro'- vided with an electricallyoperated oil burner B controlled by a room thermostat T through arepulsion relay R and safety switch bulb iof the type shown in Figures 8and 9. An electromagnetic means is employed to re-set the switchingmechanism with the bulb I by arranging an electro-magnet EM adjacent thewall of the bulb I aligned with the armature 59 of the re-set mechanism.The-electric current for energizing the electro-magnet EM is preferablyderived from the commercial source by interposing in the wire-L amanually operable switch which normally completes the circuit from thesource through wire L to binding post 3| connected to the motor switchMS and primary coil PC of the repulsion relay R. This switch preferablyincludes a manually depressible plunger P having a bridge 62 normallyheld in engagement, with spaced apart contacts 63 and connected to thewire L to complete the' circuit during normal operations of the systemand corresponding contacts 64 spaced apart from each other and fromcontacts 63 adapted to be engaged `by the bridge 62 when the'plunger Pis depressed. One of the contacts 64 is connected.r

65 .itc 'bindinglpost to connect litto dwire 'has been Vactuated toAYopen `vthe Jcircuit lthroughthe 'mercury' =B in the bulb lllby failure:of 4"comloustion', land the operationof Elthe lbl-irn'er "mechanismvceases, the vllsaietyswitch mechanism within lfthe ihulb l xnay'be're-set by 'manually depressing Athe plunger P'fto cause ithe bridge' 62to connect 'the contacts iM, as shown :in Idotted lines 'Figure im. Acircuit Lfromr -wire iL iis 1theniestablished through l:theelectro-magnet EM to Wire ILL-itc energize theielectro-magnet EMwhichiinturn attracts ithe far-mature `59 .to immerse the fend olf-,electrodeex- 'tension flll `in the mercuryrl and allow the latch lr4 'Ito`maintain l"the .'fcircuit through the #mercury 6 hy `.riding .lover`the l shoulder f28. @Releasing fthe plungerP .causes :the :commercial:circuit to lhe againV closed ithrough `bridgelli2 vland ,contacts 63lthebinding :post `3 I hln :the :event [that 'lthe plunger P ffails ltoreturn' .to its lmormal .position :afterimanual operation, :the circuit`,to l.the relay .*Rfand motoriswitchaMSiwill .remain open .and the`lliurner mechanismfwvillwnot be able .to .operate `while .fthegelectronnagnei'. remains energized.

"F.in fthe ..form shown :in :Figure .lllfthe safety switch bulb lismounted :in :ahousinglHorming a fpart mf. the fair. pine :of lv,the:burner B fin such qa :manner ithat :the `.rays of` light :emanating:from `.the :burning fue'l Willfentertheopen.endxof the .air :pipe .and'fall upon. the :reflector fla :of the bullo il :It :can ireadi-ly ibeunderstnod that 'in :a switch constructed in .accordance with the iaboyexde -scriptonthe coil responsive to relectrical'ly :gen- .era'ted heatand-'the coilresponsivetorlight rays may :beso `ico-,ordinated:atthafactory thatin response l"to-:their respective sources ,of heat theimovementaof :one :normally neutralizes 'the move- ;mento'f the other.-Anylappraciable -yariation in the :current V,yalue in :the electrically,heated :eleunent'will vary the lheating .of -.that selement and themovement thereof so that the movement of the :other `-element responsiveto light will fail to lform :of a coil it vmay `"oe `attached'as an*integral vpart lof 4the switch structure at Jthe lfactory "to eliminateany possible omission fof the balla'st 'wnenthe switch-reinstalled.`Ilrom the drawings.andidescriptionsfof the various forms of switches:disclosed herein, it Tis apparent that lthese switches may 'be employedas control tdevices depending upon vthe existence 4'of light .upon whichthe 'switch i'is focused ito main- `tain the switch inclosed circuitpositionl while 'the'circuit to the switch isclosed, i-whereby `.whenuthe source `'of 'light 'is `removed, the continued-passage of thelcircuit through the switch `will .open it. `It is also seen that vtheswitch containsadditional mechanism, which may be :actuated-from a pointexterior A'of the switch, to 'ireclose 4l'the "switch circuit and thatthe switch mechanism iis Vvunaffected Iby changes -fin ambienttemperature.

provide the compensating movement necessary to maintain the circuitclosed during normal operation.

When this switch is used as a safety control in a fluid fuel burnersystem it is desirable that the operation of the safety switch beuniform irrespective of variations in line voltage within at least 25%above or below the normal voltage. In the installation illustrated inFigures 5 and l0 the relay controlling the operation of the motor switchmay be arranged to provide a constant n current in the secondarythroughout the operative voltage range in the line, and as theelectrically heated element of the switch is connected in secondarycircuit the 'current will be constant. If it is not desirable to utilizethe relay itself to regulate the current or another type relay isemployed, a ballast in the form of electrical resistance may beinterposed in the circuit of the elec trically heated switch element asshown in Figure 10. It is preferable to use nickel wire for the ballastas it possesses the characteristic of increasing its resistance as itstemperature increases and may serve to regulate the current passingthrough the safety switch, or any other Well-known resistance may beused to allow more current to flow through the safety switch as thenormal voltage decreases during a fluctuation, or vice versa. Ifresistance wire is employed in the It is also to be -fno'ted ithatthenormal posi.- tion of the switch fis in closed position, whereby the-operating parts are fin :effectbraced --ands'taf lbilized. by eachother 'to -render the structureca- 'pable fof 'withstanding ftheijarsand rough :handling, to which it :might hezsubjected, Without"distortion-and disarrangernentio'ffthe parts. This arrangement is`particularly advantageous *when the parts `vare 1necessari-lyv.constructed of thin aand 'light -we'ight ymaterials lin order Cto.contrnland `the responsive tofsmall ycurrent fsuch :as 'may lexist iin`fthe llow, voltage -fcircuiiI :disclosed :in EEigure 25.

It iis also ito be :noted that fthe .movable welec vtrode ll `docs'-'ndtjust engage Y"the'.surfaceiliut.:is immersedlin the body o'f mercury 6:containedfin the well. This varrangement permits :the .switch'to'be'ltiltedf considerablyiin various :directions vfrom the-vvertica-l 'without displacing the lmercury :in vthe -Wellrsufficiently to :prevent rcontact athere.- Withbythe'movablaelectrode lThis :particular :switch construction lis :especially advantageous foruse vsin :connection with electrically operated'and'icontroHed fiuid.ifuel burners in railway 'locomotives :or in zany `other place wherethere is a considerable .vhrationfand `pitching or frolling 'motion'asuch fas ...occurs with `rnarine apparatus.

1. 'an electricallykoperatedand controlled fluid fuel burner heatingsystem including a burner motor, a circuit therefor, an electricallyactuated motor switch in the burner circuit, actuating mechanismincluding a controlling circuit for the electrically actuated motorswitch, a safety switch responsive to the light of the burner flameinthe controlling circuit, said safety switch including a thermallyactuated mechanism normally maintaining a closed circuit through theswitch and operating, upon the closure of the controlling circuit, toopen said circuit upon initial or subsequent failure of the burnerflame, but upon establishment of the burner flame to continue tomaintain said closed circuit and a remote-controlled mechanismcooperating with said thermal mechanism and associated with the motorswitch actuating mechanism to be operable to reset the safety switchwhen the motor switch circuit is open. y f

2. In an electrically operated and controlled duid fuel burner `heatingsystem including a burner motor, a circuit therefor, an electricallyactuated motor switch in the burner circuit actuating mechanismincluding, a controlling circuit for the electrically actuated motorswitch, a safety switch responsive to the light of the burner mallymaintaining a closed circuit through the switch and operating, upon theclosure of the controlling circuit, to open said circuit upon initial orsubsequent failure of the burner flame, but upon establishment of theburner name to continueto maintain said closed circuit and wherein thesafety switch thermal mechanism is electrically responsive to reset theswitch to its normal closed position after it-has been opened,

a remote controlled mechanism for electrically y `energizing saidthermal mechanism to reset the switch and associated with the motorswitch actuating mechanism to be operable when the motor switch is openand inoperable when the motor switch is closed.

flame in the controlling circuit,-said safety switch including athermally actuated mechanism normally maintaining a circuit closedthrough the switch and operating, upon theY closure of the i controllingcircuit, to effect the opening of said circuit upon initial orsubsequent failure of the burner flame, but upon establishment of theburner 'iiarne .to continue to maintain said c'ircuit closed, saidsafety switch thermally actuated mechanism including an electricallyactuated reset member to reset the switch to its normal closed positionafter it has been opend, a remote controlled mechanism for energizingsaid reset member and associated with the operation of the motor switchactuating mechanism to allow energization of the reset memberuponopening the motor switch. z

5. The structure of claim, wherein the actuated reset member includes anarmature, an electro-magnet to cooperate therewith, said electromagnetbeing in a circuit controlled by said remote control mechanism, thelatter being amanl ually operated switch adapted in one position .toclose a circuit to the electro-magnet andin another the circuit to themotor switch mechanism.

6. The structure of claim 4, wherein the thermally actuated mechanism iscontained within an enclosed transparent bulb, a body of mercurytherein, two electrodes one of which is normally movable and adapted toenter into and be withdrawn from the mercury to close and vopenthecircuit therethrough, resilient means normally withdrawing the movableelectrode from'the mer- .curyto open the switch, electrical means for actuating the movable electrode to enter into Ythe mercury to close theswitch, a releasable latch for engaging and holding the movableelectrode when the switch is closed, a latch release for operating thelatch to release 'the movable electrode, a thermally actuated mechanismfor operating the latch release, said mechanism being responsive to twosources of :heat which, when both prevail, render said mechanisminoperative, one of said sources being the light of the burner flame andthe other Vtheresistance of a part of the switch to the passage ofcurrent therethrough, the latter, upon' failure of the burner flame,acting to operate the mechanism to cause the releasable means to releasethe movable electrode to open the switch.

7. The structure of claim 4, wherein the electrically actuated resetmember comprises an ambient temperature compensated thermal resetactuator interposed in the switch structure to place a movable portionthereof in closed or open circuit position, an electric heater therefor.en ergized through the remote controlled mechanism, said thermal resetactuator when heated establishing a closed switch circuit and when coldan open circuit and wherein the thermally actuated mechanism, innormally maintaining the circuit closed through the switch, effects thesame by opposing the action of the thermal reset actuator to open theswitch circuit when cold, after the closure thereof.

IRA E. McCABE.

